The present invention relates in general to lasers, and in particular, to an improved, more efficient laser pumping apparatus.
It has long been recognized, as in Keefe, Jr. U.S. Pat. No. 3,611,190 issued Oct. 5, 1971, that the amount of pumping energy entering the body of a laser element is related to the extent of exposed laser element surface area on which the pumping energy impinges. However, the energy absorbed from the pumping source produces heat in the laser element which becomes more difficult to dissipate as the cross section or diameter of a laser rod is increased in order to increase the surface area. Moreover, it has been recognized, as in Keefe, Jr. that changes in temperature in the laser element cause unequal indices of refraction across the lateral extent of a laser rod because of the linear expansion of the element or material.
Although face pumped disc lasers, as opposed to side pumped rod lasers, provide a greater active surface area exposed to the pumping source while minimizing the heat problems, the face pumped lasers disc have the disadvantages of there being more "walking off" of the optical waves and a greater spread of the resulting laser light beam. Keefe, Jr. teaches a segmented laser rod immersed in coolant fluid with a segment spaced apart a sufficient distance to permit free passage of sufficient coolant but close enough to prevent pump light from passing through the spaces between the segments as a solution to the recognized problems.
Martin, U.S. Pat. No. 3,581,229 issued May 25, 1971 discloses a face pumped laser with a prism disposed between the pumping source and the face of the laser element. The prism in the Martin disclosure is of the Porro type having one right angle and two forty-five degree angles and is fabricated from fused silica having an index of refraction greater than the square root of two. The pumping source includes an array of xenon flash lamps parallel to each of the two surfaces of the prism not adjacent the active surface of the face laser element. The area of the surface of the prism adjacent the active surface of the laser element forms a forty-five degree angle with each of the two surfaces that are exposed to the pumping source and which themselves meet at a ninety degree angle. Consequently, the pumping flux density in the Martin device is increase by the square root of two over pumping apparatus not employing the prism. However, the Martin device requires precise geometric alignments among the pumping source, the prism and the surface of the laser element and does not lend itself to use on a side pumped laser rod in which the pumping energy impinges upon the curved cylindrical surface of the rod.
Sturel U.S. Pat. No. 3,974,454 issued Aug. 10, 1976 discloses a side pumped laser rod having the shape of a cylinder of revolution whose shape is obtained by the rotation about an axis of an arc of a curve turning its convexity toward the axis which is then surrounded by a liquid having a refraction index close to that of the rod and which is kept in place by a tube made of a material transparent to the radiation emitted by a flash lamp. The purpose of the Sturel laser amplifier is to decrease the detrimental effect of the diffraction caused by the passing of the radial gaussian beam through the laser element comprising the rod and liquid. Sturel has the recognized disadvantages of requiring the specially shaped rod and surrounding it with a liquid having a like refraction index. Moreover, while Sturel is suppose to result in a beam having an even density of power at the output of the amplifier, it does not result in a laser that makes more efficient use of the pumping source.
Maiman U.S. Pat. No. 3,353,115 issued Nov. 14, 1967 discloses in the embodiment illustrated in FIG. 6 the filling of the space between a laser rod and a hollow flash tube with fluorescent material that absorbs "white" light emitted by the flash tube and re-emits predominately green light that is said to be more efficiently absorbed by the laser rod.
Lewis et al. U.S. Pat. No. 4,228,406 issued Oct. 14, 1980 teaches packing glass spheres or balls that are doped to absorb radiation at the wavelength of spurious or parasitic emissions around the curved edge of a face pumped laser disc to absorb or attenuate parasitic or spurious emissions which are in directions transverse to the path of the radiation through the laser disc as well as physically supporting the laser disc.
It is thus an object of the present invention to provide an improved laser pumping apparatus that may be readily assembled for effectively increasing the active surface area of the laser element to increase the efficiency of transmission of the pumping energy from the pumping source to the laser element.
It is a further object of the subject invention to provide an improved laser pumping apparatus comprised of a plurality of generally spherical beads disposed in pumping energy transmitting juxtaposition with at least part of the active outer surface of a laser element between the pumping source and the active outer surface.
It is also an object of the present invention to provide an improved laser pumping apparatus in which at least part of the active outer surface of the laser is coated with a pumping energy transmitting adhesive and the generally spherical beads are disposed in contact with the adhesive to secure the generally spherical beads in pumping energy transmitting juxtaposition with the active outer surface of the laser element.
An additional object of the present invention is to provide an improved laser pumping apparatus in which a plurality of generally spherical beads are secured to an intermediate pumping energy transmitting member which is then mounted on the active outer surface of the laser element between the pumping energy source and the active outer surface.
These and other objects of the invention will become apparent in light of the present specification, drawings and claims.